The Combustion of Polymers

Introduction

The history of polymers stretch back millions of years. These “primitive” polymers were created by nature to fulfill the needs of information storage, energy storage and information reproduction. Human made polymers are a more recent invention, of the last two hundred years or so. These polymers are general made of highly flammable hydrocarbons and their derivatives. Fires caused by a combination of human careless and the physical properties of hydrocarbons have caused millions of dollars in property damage and claimed an untold number of human lives. It is this fact that has lead to scientists devoting time and resources to making polymers safer. In the following paragraphs the mechanism behind burning polymers will be discussed, as well as the techniques employed to either slow the rate of fire and/or extinguish it altogether. A section will also be devoted to a review of ongoing, within the last five years, research into enhancing the flame retardancy of polymers.

The combustion of a polymer can be classified as an exothermic oxidation reaction. The reaction starts when the polymer is heated to its initiation temperature or when the chemical bonds begin to cleave. As a result, the polymer begins to give off volatile gases (reducers), which mixes with atmospheric oxygen (oxidizer). When this fuel mixture either reaches their autoignition temperature or are exposed to an external source of energy, they undergo combustion or the oxidation reaction. Of which the products are water, carbon dioxide and heat. Although most of the heat is radiated into the surrounding environment, some of it will be used to initiate further polymeric decomposition. The oxygen that was used is replenished via the convection current gener...

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...ed structure. For this series of experiments, the group changed the synthesis method, changing the small molecule surfactant to a cationic copolymer (PVAc). They did this so they can control the morphology of the resulting polymer complex. As a result of this change, the physical properties of polymers with the inclusion of this copolymer was undertaken. They found for the control groups EVA-0 and EVA-NC0, that both the Young's modulus and tensile strength increase and the toughness decreases when compared to the value for unmodified EVA. The toughness rebounded when clay was added. This is opposite to what is expected, as the copolymer is more amorphous than EVA. If the trend was followed the Young's modulus and tensile strength should decrease while the toughness increases. The authors contribute this opposite trend to the fact that the copolymer has Tg than EVA